1. Field of the Invention
The invention relates to a sliding door with a magnetic carrying and/or drive system with a permanently excited magnetic carrying device and a linear drive unit with at least one row of magnets, in particular for an automatically operated door. The term “row of magnets” includes oblong individual magnets as well. The row of magnets can be stationary or non-stationary.
2. Description of the Related Art
A sliding door guide is known from DE 40 16 948 A1, wherein, under normal load, magnets interacting with one another effect a contact-free floating guidance of a door leaf or the like, which leaf is maintained in a sliding guide, in addition to the stationary disposed magnets in the sliding guide, a stator of a linear motor being provided, the rotor thereof being disposed at the sliding door. On account of the selected V-shaped disposition of the permanent magnets of the disclosed permanently excited magnetic carrying device, a laterally stable guiding path can not be realized, hence a relatively complicated disposition and embodiment of stator and rotor are required. This arrangement raises the price of the such a sliding door guide considerably.
A combined support and drive system for an automatically operated door is known from WO 00/50719 A1, wherein a permanently excited magnetic carrying system is symmetrically designed and has stationary and non-stationary rows of magnets, which are respectively disposed in one plane, the carrying system being in an unstable equilibrium, and wherein the carrying system has symmetrically disposed lateral guiding elements, which may have roller-shaped supports. The laterally stable guiding path thus achieved results in a simple development and disposition of stator and rotor of a linear motor accommodated in a common housing, namely the option of being able to arbitrarily dispose the stator and the rotor of the linear motor in relation to the carrying system and of experiencing no limitations by the carrying system as to the shape of stator and rotor.
These two support systems have in common that they function according to the principle of repulsive forces, which principle of action allows for a stable poise without requiring an expensive electrical control device. However, the drawback therein is that both at least one stationary and at least one non-stationary row of magnets need to be provided, i.e. magnets need to be disposed along the whole path of the sliding guide or of the bearing of the automatically operated door and at the carrying slide for the door, which slide is movable along this guide, thus making the production of such system very costly, which on the other hand, is characterized by an extremely soft-running and silent operation and is almost wear-free and maintenance free, as the mechanical friction necessary for carrying the door has been obviated.
Another electromagnetic drive system for magnetic floating and carrying systems is known from DE 196 18 518 C1, wherein a stable floating and carrying state is achieved through an appropriate disposition of a permanent magnet and ferromagnetic material. For this purpose, the permanent magnet brings the ferromagnetic material in a state of partial magnetic saturation. Electromagnets are disposed such that the permanent magnets are moved exclusively by changing the saturation in the carrying rail, and the coil cores are included in the permanent magnetic partial saturation, which results in the floating and carrying state.
WO 94/13055 further shows a stator drive for an electric linear drive and a door, which is equipped with such a stator and suspended by means of magnets from the door lintel of a frame. For this purpose, several magnets or groups of magnets are disposed at the door panel, their magnetic field strength being so important that an attractive force to a guiding plate disposed at the underside of the door lintel is achieved, whereby this attractive force is sufficient to lift the weight of the door panel.
On account of the selected dispositions of the magnetic support and/or the magnetic drive, the forces to be overcome in all these systems for starting acceleration need to be greater than those, which have to applied for continuing the motion of the moving door, and the force required for displacement along the travel path is “rippled”.